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```									         Fun Physics You Can See
Lasers, Holograms and Spectroscopy

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The Inside Scoop on Light

•Light is a wave, kind of like a wave in the ocean

•These light waves carry energy. This energy can do many interesting
things, like help grow a plant, produce electric currents, or cause
chemical reactions.

•Light carries a different amount of energy depending on its wavelength.
Wavelength: the Secret to the Rainbow
• Light that has a longer
wavelength appears more red,
and light that has a shorter
wavelength appears blue.

• The shorter the wavelength,
the higher the energy carried
by the wave.

• You may have heard of
“ultraviolet” or “infrared” light.
That is light at either extreme
of wavelength, very short
(ultraviolet) or very long
(infrared).

• Our eyes cannot always detect
light if the wavelength is very
long or very short.
Diffraction Gratings:
The Bending of Light
• A wave is bent when it hits a rough
surface or passes through a small
opening, or aperture. This is called
diffraction. Diffraction happens to
all types of waves, including light.

• The white light we see from the sun
and light bulbs is not really white. It
is made up of many different colors.
These colors that make up the light
are known as a spectrum. If you
have ever seen a rainbow, then you
have seen the visible spectrum.

• Diffraction gratings separate light
into the different colors of light that
Spectroscopy:
The Finger Prints of Elements
•Spectroscopy is the
study of the spectrum
from different atoms
and molecules.

• Electrons in an atom can get
excited. An excited electron is
in a state of high energy.
Sometimes these electrons
jump down to a state with low
energy. The difference in
energy is given off as light.

• Since different kinds of light
have slightly different spectra,
scientists can use a star's
spectrum to figure out what
Phosphorescence: A Big Word for
Glow-In-the-Dark
Certain compounds contain things called phosphors.
•Phosphors emit visible light when
exposed to energy, like from ultraviolet
light. They do this because of electrons
jumping between energy states.
•In order to give the electrons enough
energy, you have to use light with a
short wavelength.

•Some phosphors, like the
ones in fluorescent lights,
do not glow after the energy
source is taken away. Those
that continue to glow after
the energy is taken away are
called phosphorescent.
Light Can Carry a Lot of
Information

• Holograms and fiber optics are two methods of information transfer
that use light.

• Holograms are made using lasers to record a 3 dimensional object
on a 2 dimensional surface, like a piece of paper. Our eyes see the
object because of controlled use of diffraction.

• Fiber optics is a method of sending information as light through a
cable. This light signal can be changed to music, video and more!
Fun Facts
• A hologram the size of a sugar
cube could hold enough
movies!
• CD’s, like holograms, use
diffraction patterns to store
information.
• Light from the sun can be
transformed into usable energy
to power homes, cars and
more.
• Light at the far ends of the
spectrum, like microwaves
(far into the infrared) and
gamma rays (far into the
ultraviolet) have some very
interesting properties. You